1. Field of the Invention
The present invention relates to a receiving apparatus for receiving a television broadcast program via a plurality of different media, in which the display content can be switched at any time desired by a broadcast station. In particular, the present invention relates to a receiving apparatus capable of controlling a streaming program provided by a television broadcast station based on an event message or the like to offer a commercial message (CM), etc., to all subscribers at arbitrary times and capable of seamlessly switching between the streaming program and the CM.
2. Description of the Related Art
With the development of technologies such as ADSL (asynchronous digital subscriber line), cable TV, and optical fibers, high-speed Internet access services, called broadband services, have rapidly become widespread. Current broadband services support communication rates as high as 512 Kbps (kilobits per second) to several Mbps (megabits per second).
The communication rate of traditional dial-up Internet access via analog telephone communication is no more than about 28.8 to 56 Kbps. The communication rate of general ISDN (Integrated Services Digital Network) services capable of digital transmission of communication data is from 64 Kbps to 128 Kbps. The communication services at communication rates no more than 128 Kbps make it difficult to provide real-time transmission of TV or VHS-quality video signals, whereas broadband services sufficiently support practical use of video transmission, etc., and have the potential for making greater use of the Internet or personal computers (PCs). Japanese Patent Application Laid-Open No. 2001-318848 (US A1 20010042111) discloses an apparatus for making a request for distribution of content, downloading and recording the content, and playing back the recorded content.
One broadband service is program streaming. Streaming is a technique which enables a user to sequentially play back audio data or motion picture data stored on a server while downloading it via a network. The streaming technique can be used to play back even motion picture data having a large file size without waiting for a time-consuming download, and can also be used to distribute captured motion pictures in real time. The streaming technique in a broadband environment allows users to enjoy high-quality content on their PCs.
The demands to handle Internet content, e-mail, still images taken by a digital still camera, etc., on a television screen using a TV remote control unit, as if they were being viewed on TV, have also increased, and products meeting these demands have become commercially available. In view of such a background, viewing of streaming programs will be incorporated as a function of television receiving apparatuses. Then, even PC novices can enjoy streaming broadcasts on TV with ease.
Recently, a variety of information has been digitally transmitted, and the popularity of digital broadcasting of television programs has also increased. Digital satellite broadcasting services, such as CS (Communication Satellite) broadcasting and BS (Broadcasting Satellite) broadcasting, have already begun, and digital terrestrial broadcasting services will also start. One of the merits of digital broadcasting is information compression. Digital compression techniques allow for multiple-channel transmission using the bandwidth corresponding to one traditional analog broadcasting channel. In BS digital broadcasting, actually, a plurality of channels share a single frequency band. The number of shared channels in SD (standard definition) broadcasting is typically three to four, although it depends upon the bit rate of the content, etc.
Although digital compression techniques allow for multiple-channel transmission, the frequency bandwidth is finite. When a multiple-content program including 10 to 20 items is provided from a broadcast station, it is difficult to provide the program to users with sufficiently high definition. Therefore, the demands for broadcast stations to utilize the above-described streaming techniques to provide multi-content programs is considered.
In viewing streaming programs on a television receiving apparatus, switching between two media, i.e., broadcast waves and streaming, is important. Seamless switching will provide users with a comfortable viewing experience. On the other hand, if the switching causes the content to be interrupted, or if the switching takes a long time, users will not be satisfied with this service.